textproduct: Rapid City

KEY MESSAGES

- Active pattern persists through the weekend with daily chances of showers and thunderstorms, a few of which may be strong to severe today through Monday.

- Trending warmer to end next week.

DISCUSSION

(This Evening Through Saturday) Issued at 106 PM MDT Sat Aug 15 2026

Water vapor imagery shows shortwave trough pushing through eastern and central Wyoming this afternoon. Northwesterly low level flow persists behind a surface cold front that stretches from eastern ND through eastern SD into central NE. Isolated convection initiated this morning across NE WY with additional storms expected through the afternoon and evening across NE WY and the far southwestern portion of the forecast area. MLCAPE values ~250-750 J/kg will be in place this afternoon and evening, although effective shear will be limited (~30-35 knots or less). A few storms may be strong to severe (Marginal risk across portions of NE WY and SW SD), although overall instability and shear parameter space will will preclude more organized severe convection.

Upper level ridge flattens Sunday as upper level flow turns zonal then northwesterly into early next week. Ample instability will be in place Sunday with effective shear around 35 knots, supporting threat of transient strong to severe storms. However, upper level ascent will be weak, limiting extent of the severe threat Sunday afternoon and evening. Best chance for convection Sunday afternoon will be across the Black Hills (central and southern) given orographic lift and across NW SD where better upper level ascent will be present.

Generally westerly to northwesterly flow will persist through mid- week with near-daily chances of thunderstorms. Severe threat Monday is still uncertain and contingent upon timing of the upper wave and surface front. Sufficient shear is in place Monday (effective bulk shear 35-50+ knots) for more organized severe convection should the other ingredients fall into place.

Strong upper ridge is forecast to build over the southwestern US late next week, spreading into the Rockies and Northern Plains. Expect temperatures to warm back into the upper 80s to 90s to end the week into next weekend.

AVIATION

(For the 18Z TAFS Through 18Z Sunday) Issued At 1110 AM MDT Sat Aug 15 2026

Isolated to scattered showers and thunderstorms will be possible today/this evening. Thunderstorm development will begin around 15/18z and last through 16/06z, mainly over northeast Wyoming, the Black Hills, and southwestern South Dakota. Transient MVFR/IFR conditions are possible around any heavier precipitation cores. Conditions will improve starting around 16/08z, with mainly VFR conditions expected through the remainder of the TAF period.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.